The invention relates to a press for producing a pellet from a powdered material, for example, a metal or ceramic powder. The powdered material is filled into a mold holder of a die assembly and subsequently pressed into a pellet in the mold holder by an upper punch and a lower punch. One such a press is known, for example, from EP 2 311 587 A1. The known press has a press frame with an upper and a lower part of the press and vertical pillars, which connect the upper and lower parts of the press with one another. As precise an alignment as possible of all components in the force flux during the pressing process is of decisive importance for the result of pressing with such presses and for the wear of the press. For the known press, a plurality of components, which are usually produced individually, and component levels are in the flux of the force. As a result, the manufacturing tolerances add up and, because of the high forces of the press, components of the press may become deformed. In particular, it is possible that the axes of the upper and lower drive units, which drive the upper and lower punch, are not aligned with one another precisely. Consequently, the pressing result may be defective. In order to minimize the effects on the pressing result, it has been proposed that so-called tool guiding units be used, which comprise the upper and lower punches, as well as a die plate with a mold holder. If the tool guiding units are dimensioned adequately, the effect of deforming the press components on the pellet is negligible. However, this leads to a considerable additional expense with regard to the tool guiding units. In addition, during the pressing, there is increased wear of individual components, such as seals and guiding tapes of cylinders in the case of hydraulic presses, spindles and spindle nut units in the case of spindle presses or guides of the tool guiding units.
A further press is known from the W0 2008/104969 A1. This press has a frame-like press frame, for which an upper and a lower frame plate are connected with one another over several struts at the edge, which are oriented parallel to a longitudinal axis of the press frame and are connected with one another. Between the upper and the lower frame plate, a die plate, which is aligned perpendicularly to the longitudinal axis and in which there is a holder for pressing a powdered material, is fixed to the press frame. A pair of guiding rods, which are oriented in the direction of the longitudinal axis and are securely mounted in the press frame at a distance from one another in the upper and lower region thereof, penetrate the die plate as well as a press arrangement, which is disposed above and below the die plate, provided for accommodating and moving a press punch and can be moved on the guide rods. Each of the two threaded rods, which are anchored securely at a distance from one another in the die plate, engages an assigned threaded nut, which is mounted rotatably in the upper and the lower press arrangement, the two upper and the two lower ones being driven by a motor carried by the assigned press arrangement.
The upper and the lower press arrangement can be moved in the vertical direction over the spindle drives, which are fastened to the die plate and which, synchronized in pairs, are driven by the in each case one motor. Accordingly, the motors for operating the spindle drives are moved along correspondingly with each vertical movement of the press arrangement. The pressing force, which functions as an action force and is to be applied at the upper and lower press punch whenever the powdered material is pressed, generates a reaction force, which is absorbed over the threaded rods, which are fixed in pairs above and below to the die plate, and discharged into the die plate. This construction requires considerable dimensioning of the die plate and also of the respective press arrangement, in order to absorb the forces and moments occurring in the course of the pressing and in the course of the hereby occurring movement of the upper and lower press arrangement. In addition, for exchanging the press arrangements with their press punches, the press must be largely dismantled, no information being provided about the exchangeability of the holder of the powdered material in the die plate.
Starting out from the prior art explained above, the invention is based on the objective of making available a press of the type named above, with which, in a structurally simple manner, an optimum pressing result is achieved and, at the same time, an exchange of the components of the press in a simple manner is possible.